Fix passenv to work with tox 4

[tunetheweb]

Brief summary of the change made

tox4 changes passenv to a comma-separated list, rather than space-separated: tox-dev/tox#2658

Are there any other side effects of this change that we should be aware of?

This is only really important for CI (which uses latest tox), so think it should be OK even for v3 users.

I also removed the last remaining references to CIRCLECI that we replaced with GitHub Actions a long time ago.

Pull Request checklist

• Please confirm you have completed any of the necessary steps below.

• Included test cases to demonstrate any code changes, which may be one or more of the following:

  • .yml rule test cases in test/fixtures/rules/std_rule_cases.
  • .sql/.yml parser test cases in test/fixtures/dialects (note YML files can be auto generated with tox -e generate-fixture-yml).
  • Full autofix test cases in test/fixtures/linter/autofix.
  • Other.

• Added appropriate documentation for the change.

• Created GitHub issues for any relevant followup/future enhancements if appropriate.

[codecov]

Codecov Report

Base: 100.00% // Head: 100.00% // No change to project coverage 👍

Coverage data is based on head (dc39e38) compared to base (9cd847e).
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #4154   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files          195       195           
  Lines        14920     14920           
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  Hits         14920     14920           

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